Medicine delivery device having detachable pressure sensing unit

ABSTRACT

A fluid medicament delivery device includes a patient attachment unit and a separate indicator unit. The patient attachment unit includes a housing and a fluid channel located therein, wherein at least a portion of the fluid channel includes a flexible member substantially coterminous with the housing. The separate indicator unit is adapted to be detachably coupled to the housing of the patient attachment unit and includes a first sensing element for contacting the flexible member when the indicator unit is coupled to the housing to sense a flexure of the flexible member.

FIELD OF THE INVENTION

This invention relates generally to medicament delivery devices and,more specifically, to medicament infusion devices that utilize areusable indicator unit and a disposable medicament-delivery unit.

BACKGROUND

Medicament infusion devices are utilized to deliver liquid fluidmedicine to patients. For example, insulin infusion devices are oftenused by persons with diabetes to maintain adequate insulin levelsthroughout the day or to increase insulin levels during mealtime. Theseinsulin infusion devices can replace the syringe-based injections commonamong those with diabetes.

Insulin infusion devices are available in several forms, and includeseveral common components. Generally, an infusion device includes ahousing that may be worn on a patient's clothing (a belt, for example)or on the patient himself, and that contains a number of mechanical andelectrical components. A reservoir holds the insulin and anelectro-mechanical pump mechanism (various types are used) delivers theinsulin as needed to the patient. Battery-powered electronics controlthe pump and ensure that the device is operating properly. Varioussensors communicate with the electronics and other components to detectocclusions, sound alarms, measure remaining insulin capacity, etc.

While these devices are useful, they do suffer from severalshortcomings. First, the high expense of the devices makes themaccessible to fewer people than the diabetic population members who maybenefit from their use. Second, failure or malfunction of one componentrequires repair or replacement of the entire device, a costly scenario.For example, if the pump fails, often the entire unit (including theproperly functioning—and expensive—electronics) must be replaced. Third,over time the device gets dirty due to repeated uses, which requiresperiodic cleaning and may cause a failure condition at a later date.

SUMMARY OF THE INVENTION

What is needed, then, is a medicament infusion device that utilizeslow-cost components, some of which may be replaced periodically afteruse, without having to dispose of other expensive, but operational,components in the device.

In one aspect, the invention relates to a fluid medicament deliverydevice having a patient attachment unit that includes a housing and afluid channel located therein, such that at least a portion of the fluidchannel has a flexible member substantially coterminous with thehousing. The fluid medicament delivery device includes a separateindicator unit adapted to be detachably coupled to the housing of thepatient attachment unit. The indicator unit includes a first sensingelement for contacting the flexible member when the indicator unit iscoupled to the housing, such that the first sensing element senses aflexure of the flexible member. In an embodiment of the foregoingaspect, the indicator unit also includes a second sensing element forsensing a pressure external to the housing. In another embodiment, thepressure external to the housing includes an ambient pressure.

In an embodiment of the above aspect, the first sensing element includesa pressure sensor. In another embodiment, the first sensing element alsoincludes at least one of a fluid and a gel adapted to contact theflexible member, such that the flexure of the flexible member istransmitted by the at least one of the fluid and the gel to the pressuresensor. In yet another embodiment, the separate indicator unit defines awell for containing at least one of the liquid and the gel. In stillanother embodiment, the separate indicator unit includes a raised lipsurrounding the well, such that the raised lip is disposed above aproximate portion of the separate indicator unit. In another embodiment,the raised lip is adapted to contact the housing of the patientattachment unit.

In another embodiment of the above aspect, the second sensing elementincludes a pressure sensor adapted to sense the pressure external to thehousing, and at least one of a fluid and a gel adapted to transmit thepressure external to the housing to the pressure sensor. In anembodiment, the housing has a hermetically-sealed housing defining aninterior space and including at least one substantially flexible housingportion. The substantially flexible housing portion is adapted fortransmitting the pressure external to the housing to the interior space.In still another embodiment, the substantially flexible housing portionis located on a portion of the patient attachment unit facing theseparate indicator unit and the second sensing element is located on aportion of the separate indicator unit facing the patient attachmentunit, when the patient attachment unit is coupled to the separateindicator unit.

In yet another embodiment of the foregoing aspect, the patientattachment unit is adapted for adhesion to a skin surface of a patient.In an embodiment, the fluid medicament delivery device also includes aprocessor adapted for interpreting a signal from a pressure sensor, suchthat the signal is sent to the processor based at least in part on theflexure of the flexible member.

In another aspect, the invention relates to a method of monitoringpressure within a fluid channel of a fluid medicament delivery device,the method including measuring an actual pressure of a fluid within thefluid channel, comparing the actual pressure to a pressure rangeincluding a maximum pressure and a minimum pressure, and sending anotification when the actual pressure is outside of the pressure range.In an embodiment, the method also includes measuring a pressure externalto the fluid medicament delivery device.

In an embodiment of the above aspect, the method of monitoring pressurewithin a fluid channel of a fluid medicament delivery device alsoincludes modifying the actual pressure based on the external pressure toobtain a corrected pressure, and comparing the corrected pressure to thepressure range. In another embodiment, the method also includesmodifying the maximum pressure and a minimum pressure of the pressurerange based on the external pressure to obtain a corrected pressurerange, and comparing the corrected pressure range to the actualpressure. In still another embodiment, when the actual pressure exceedsthe maximum pressure, the notification includes at least one of adownstream occlusion notification and a near-empty reservoirnotification. In yet another embodiment, when the actual pressure isless than the minimum pressure, the notification includes at least oneof an upstream occlusion notification and an empty reservoirnotification.

In another aspect, the invention relates to a method of manufacturing apressure sensing element, the method including securing a pressuresensor to a base, securing a template defining a well therein to thebase, such that the pressure sensor is located in a bottom portion ofthe well. The method includes filling at least partially the well with agel having a substantially liquid state, so that the well includes afilled portion and an unfilled portion, and the filled portion and theunfilled portion are characterized by a presence or an absence of gel.The method includes solidifying the gel in the filled portion to asubstantially gelled state, and filling the unfilled portion with a gelhaving a substantially liquid state.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the present invention, as well as theinvention itself, can be more fully understood from the followingdescription of the various embodiments, when read together with theaccompanying drawings, in which:

FIG. 1 is a schematic top view of a fluid medicament delivery device inaccordance with one embodiment of the invention;

FIG. 2 is a schematic side view of the fluid medicament delivery deviceof FIG. 1;

FIG. 3 is a schematic diagram of an exemplary infusion devicemicro-fluidic circuit in accordance with one embodiment of theinvention;

FIG. 4 is a schematic bottom view of a patient attachment unit of thefluid medicament delivery device of FIG. 1 with an external housingremoved;

FIG. 5 is a schematic perspective view of an indicator unit of the fluidmedicament delivery device of FIG. 1 with an external housing removed;

FIG. 6 is a schematic exploded perspective view of the indicator unit ofFIG. 5;

FIG. 7 is a schematic top view of the patient attachment unit of thefluid medicament delivery device of FIG. 1;

FIG. 8 is a schematic bottom perspective view of the indicator unit ofthe fluid medicament delivery device of FIG. 1;

FIGS. 9A-9D depict a procedure for mounting the indicator unit to thepatient attachment unit in accordance with one embodiment of the presentinvention;

FIG. 10 is a schematic section view of the fluid medicament deliverydevice of FIG. 1 taken along line 10-10;

FIG. 11 is a partial schematic section view of a well of FIG. 8 takenalong line 11-11;

FIG. 12 is a schematic section view of a fluid medicament deliverydevice in accordance with another embodiment of the present invention;and

FIGS. 13A-13C depict a procedure for utilizing a fluid medicamentdelivery device in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION

FIGS. 1 and 2 depict an embodiment of an assembled fluid medicamentdelivery device 100 having at least two modules, a patient attachmentunit 110 and a separate indicator unit 120, each having a housing 110 a,120 a, respectively. The depicted fluid medicament delivery device 100,when assembled, defines a substantially oval shape, although othershapes (circular, oblong, elliptical, etc.) are also contemplated. Ingeneral, an assembled device having round corners, smooth edges, etc.,may be desirable, since the device is designed to be worn on the skin ofa patient, underneath clothing. Other aspects of the device that make itgenerally unobtrusive during wear include a small size (only aboutseveral inches across) and a low profile. Other device shapes and sizesare also contemplated.

The patient attachment unit 110 includes a bolus button 268 fordelivering a dose of fluid medicament, as described below. A cannulainsertion device (See FIG. 13A) inserts a cannula through the device110, subcutaneously through the skin S of a patient. Cannula insertiondevices are described in U.S. patent application Ser. No. 12/250,760,filed Oct. 14, 2008, the disclosure of which is hereby incorporated byreference herein in its entirety. After insertion, the cannula insertiondevice is disconnected from the patient attachment unit 110, and a cap112 is used to seal the opening to prevent ingress of contaminants,moisture, etc. The separate indicator unit 120 includes an indicatorbutton 122. A textured edge 124, may be present on all or part of theedge of the housing 120 a to provide a gripping surface duringattachment and/or disconnection of the indicator unit 120 and thepatient attachment unit 110, as described in more detail below.Alternatively or additionally, the edge of patient attachment unithousing 110 a may also be textured.

The patient attachment unit 110 is connected to and in communicationwith the separate indicator unit 120, as described in more detail below.The housings 110 a, 120 b of the patient attachment unit 110 and theindicator unit 120 meet at a curved interface 114. Interfaces havingother mating shapes are also contemplated. The bottom surface of thepatient attachment unit 110 includes a patient attachment interface 116.The patient attachment interface 116 may include one or more adhesivepads secured to the bottom surface of the patient attachment unit 110for adhering the fluid medicament delivery device 100 to the skin S of apatient during use. The interface 116 may comprise any suitableconfiguration to adhere the patient attachment unit 110 to the skin S.In one embodiment, the interface 116 includes a plurality of discretepoints of attachment. Other embodiments utilize concentric adhesivecircles or ovals.

The indicator button 122 may be used by the patient to test thefunctioning of the fluid medicament delivery device 100 or to cancel anotification presently being delivered or to prompt for a repetition ofa previous message or other information stored by the indicator unit.Actuating the indicator button 122 may initiate one or more tests toindicate to the patient various operational or therapy states of thedevice 100, such as whether the separate indicator unit 120 is properlymounted to the patient attachment unit 110, whether an internal batteryhas sufficient power for continued use, and/or whether pressure sensingwithin the device 110 is operating properly. Other tests are alsocontemplated. A single indicator button, such as that depicted in FIG.1, may be used to run one or more tests. The medicament delivery device100 may be programmed to recognize patterns of actuations of theindicator button to initiate certain test routines. That is, twoactuations in quick succession may initiate a “Battery Power Available”test routine, three actuations in quick succession may initiate a“Pressure Sensor Check” test routine, etc. Other combinations of shortactuations and long actuations (e.g., Short, Long, Short; Long, Long,Short, etc.) are also contemplated to initiate any number of testroutines. Alternatively or additionally, two or more buttons or otherinput features may be included on the device, for initiating one or moreseparate tests. Positive or negative feedback of the test results may beprovided to the patient in the form of audible sounds of differing tonesor durations, illumination/delumination of lights, vibrations, andcombinations thereof. In certain embodiments, light emitting diodes(LEDs) may be used to illuminate the button itself or may illuminateportions of the indicator unit housing to provide feedback to thepatient. Graphical indicia or alphanumeric information may be displayedon a suitable output device.

FIG. 3 is a schematic diagram of an exemplary infusion devicemicro-fluidic circuit 250 that may be incorporated into the fluidmedicament delivery device 100 described herein. Other infusion deviceshaving micro-fluidic circuits are described in U.S. Patent ApplicationPublication No. 2005/0165384, published Jul. 28, 2005, the disclosure ofwhich is hereby incorporated by reference herein in its entirety. Themicro-fluidic circuit 250 includes a pressurized reservoir 252 that is,in this case, an elastomer bladder. Alternatively, a flexible vessel orbag compressed by a spring may be utilized. A fill port 254 is used tointroduce fluid, such as insulin, to the micro-fluidic circuit 250. Inthis micro-fluidic circuit 250, introducing insulin via the fill port254 fills both the reservoir 252 and a variable-volume bolus reservoir256. Check valves 258 prevent backflow of insulin in a number oflocations.

During use, insulin is forced from the reservoir 252 by elasticcontraction of the elastomer, through a filter 260, and into twoparallel flowpaths, a basal flowpath 262 and a bolus flowpath 264. Thebasal flowpath 262 delivers a constant dose or steady-state level ofinsulin to a patient; the bolus flowpath 264 delivers a bolus dose ofinsulin to the patient as needed or desired by the patient, for example,in conjunction with a meal. The basal flowpath 262 includes a firstpressure sensor 266A or other pressure or flow sensors in communicationwith the flowpath 262, for example, at a mid-point in the basalflowpath. In an alternative embodiment, the first pressure sensor 266Aor first sensing element 262 may be placed further upstream ordownstream in the basal flowpath, as desired. In another alternativeembodiment, a plurality of pressure sensors in communication with thebasal flowpath 262 may be utilized. A second pressure sensor 266B orsecond sensing element is exposed to ambient air pressure P. Thefunction of and relationship between the pressure sensors 266A, 266B isdescribed in more detail below. In one embodiment, the pressure sensors266A, 266B consist of micro-electronic-mechanical system (MEMS) sensors.Each MEMS sensor is about 2 mm square but sensors having differentdimensions may also be used. Both MEMS sensors are contained within theindicator unit 120. In FIG. 3, the pressure sensor 266A communicateswith a portion of the basal circuit 262 between two flow restrictors274A, 274B (e.g., microcapillaries). In one embodiment, this portionbetween the flow restrictors 274A, 274B may be a pressure sensorchamber, as described in more detail below. The pressure sensor 266Asenses pressure changes in the basal flowpath 262, which may beindicative of occlusion conditions that increase pressure therein. Thepressure sensor 266B senses changes in ambient air pressure external tothe fluid medicament delivery device 100. The pressure sensors 266A,266B are absolute pressure sensors, but a single relative pressuresensor may also be utilized. A relative pressure sensor, e.g., a gaugeMEMS sensor, may be used to replace both absolute pressure sensors.

To deliver a bolus via the bolus flowpath 264, the patient presses abutton 268 that drives a single stroke (delivering a single dose) of abolus displacement chamber 270 and opens two valves 272. The valves 272are in series for redundancy safety purposes. An optional flowrestrictor 274C regulates, in part, the fluid flow through the bolusflowpath 264. The parallel flowpaths 262, 264 join at a common channel276 just before an internal chamber or a cannula void 278. The cannulavoid 278 is formed in a cannula base 280, which allows a point ofconnection to a cannula 282. The cannula 282 extends below the skin S ofa patient, thus delivering the insulin subcutaneously. In oneembodiment, the actuation of the bolus button 268 may be sensed by theindicator unit 120 with, for example, a magnetic sensor, a Hall effectsensor, or a switch. In an alternative embodiment of the presentinvention, at least one pressure sensor may be placed in the bolusflowpath 264, thereby allowing the indicator unit 120 to sense theactuation of the bolus button 268. Conduits 284 having diameters largerthan those of the flow restrictors 274A, 274B, 274C connect the variouscomponents.

FIG. 4 depicts a bottom view of the patient attachment unit 110 showingthe internal components and structures therein, with the housingremoved. Specifically, the bottom portion of the housing 110 a, to whichthe attachment interface 116 is secured, has been removed. Theseinternal components and structures correspond generally to themicro-fluidic circuit 250, discussed in FIG. 3. The components andstructures in the patient attachment unit 110 may be disposed in orconnected to a flow manifold 300, which serves as a mounting platformfor the various components. Note that not all conduits and flowcomponents are depicted in FIG. 4, as some components may be secured tothe opposite side of the manifold 300 or formed therein.

As described above with regard to FIG. 3, insulin in the bolus flowpath264 (the bolus flowpath 264, in FIG. 4, is downstream of the labeledarrow) of the micro-fluidic circuit 250 is delivered from the elastomerreservoir 252, filtered through the filter 260, and stored in thevariable-volume bolus reservoir 256. In certain embodiment, theelastomer reservoir 252 may have a total volume of about 3200microliters; the variable-volume bolus reservoir 256 may have a totalvolume of about 180 microliters to about 260 microliters. Other volumesof the various components are also contemplated. When the fluid pressurein the elastomer reservoir 252 is greater than the fluid pressure in thevariable-volume reservoir 256, the variable-volume reservoir 256 willcontinue to fill, subject to the flow rate dictated at least by flowrestrictor 274C in the bolus flowpath 264. Downstream of thevariable-volume bolus reservoir 256 is the bolus displacement chamber270, which may store a single dose of insulin (e.g., about 5, about 10,about 20, or about 25, or greater than about 25 microliters of insulin,in various embodiments). A check valve 258 allows for free flow ofinsulin from the variable-volume bolus reservoir 256 to the bolusdisplacement chamber 270. The check valve 258 prevents backflow during abolus stroke (i.e., actuation of the bolus button 268).

Actuating the bolus button 268 opens the two valves 272 (See FIG. 3) andempties the entire contents of the bolus displacement chamber 270.Audible, visual, and/or tactile feedback may be provided to the patientto signal that a bolus has been delivered. Releasing the bolus button268 closes the two downstream valves 272. The displacement chamber 270is then refilled with insulin from the variable-volume bolus reservoir256, which is, in turn, filled with insulin from the reservoir 252. Thebolus flow rate is controlled with a fixed volume-per-stroke of bolusstimulus, i.e., a predetermined volume of insulin-per-stroke. In anotherembodiment, the bolus flow control rate also may be controlled by abolus rate flow restrictor. Also, downstream of the filter 260 is thebasal flowpath 262 (the basal flowpath 262, in FIG. 4, is downstream ofthe labeled arrow) of the micro-fluidic circuit 250. The flowrestrictors 274A, 274B are located on opposite sides of a pressuresensor chamber 302.

In various embodiments, each flow restrictor 274A, 274B has a length ina range of about 18 mm to about 35 mm. Other lengths of the flowrestrictors are also contemplated, for example, from about 10 mm toabout 20 mm. The various channels 284 in the manifold 300 may be formedby, for example, laser cutting, and the flow restrictors 274A, 274B maybe placed therein. The flow restrictors 274A, 274B may be glued or fusedinto the channels, though other methods of retention are alsocontemplated. Exemplary flow restrictors are described in U.S. PatentApplication Publication No. 2006/0054230, the disclosure of which ishereby incorporated by reference herein in its entirety. The flowrestrictors 274A, 274B are connected to and in fluidic communicationwith a pressure sensor chamber 302 that includes a flexible member orsensor membrane 302 a (See FIG. 7) disposed thereon. The sensor membrane302 a may be generally coterminous with a mating mounting platform 404(See FIG. 7) of the patient attachment unit 110, as described in moredetail below. As the insulin in the basal flowpath 262 flows into thechamber 302, pressure of the insulin within the basal flowpath 262displaces the sensor membrane 302 a. This displacement is sensed by thepressure sensor 266A, as described below. In this manner, the pressuresensor 266A may sense the pressure of the insulin in the basal flowpathvia movement of the sensor membrane 302 a.

FIG. 5 depicts a schematic perspective view of the indicator unit 120with the top exterior housing 120 a removed. FIG. 6 shows an explodedview of the indicator unit 120 depicted in FIG. 5. As discussed herein,the indicator unit 120 may, in certain embodiments, detect changes inpressure within the micro-fluidic circuit 250 contained in the patientattachment unit 110, and perform other tests to ensure proper operationof the medicine delivery device 100. The patient may be alerted asnecessary via audible, visual, and/or tactile (e.g., vibration) signals.The components to detect pressure changes, process information, andgenerate signals or alerts to the patient are contained within theindicator unit 120.

The internal components of the separate indicator unit 120 are mounted,either directly or indirectly, to a mounting platform 350, which, in oneembodiment, may be the bottom surface of the indicator unit 120.Partially shown extending from the underside of the indicator unit 120is at least one circular mating projection 352, which is configured tomate with the patient attachment unit 110, as described below. Mountingarms 354 defining hollow interiors are disposed at or near the edges ofthe mounting platform 350. The mounting arms 354 correspond to andconnect to the top exterior housing 120 a with screw, snap-fit, press orother types of connections. Also disposed on the mounting platform 350are a supercapacitor 358, a vibrating motor 360, and two wells 362, 364.Each well 362, 364 defines a hollow geometrical structure, e.g., acylinder. Overlaid on at least the wells 362, 364 is a printed circuitboard (PCB) 366, which may include one or more processors, as well as atest switch 368 disposed thereon. Several apertures 370 formed in thePCB 366 correspond to and align with extensions 370 a from the mountingplatform 350. The extensions 370 a may be melted during manufacturing tosecure the PCB 366 thereto. The indicator button 122 aligns verticallyover the test switch 368. A piezoelectric sounder 374 or othersound-generating component is located proximate the PCB 366. One or morebattery holder solder pins 376 also penetrate the PCB. An activationswitch 378 interacts with an activation button 380, which contacts anactivation projection 428 (FIG. 7) on the patient attachment unit 110.

FIG. 7 depicts the patient attachment unit 110 and FIG. 8 depicts theunderside of the indicator unit 120. The elements that allow for theconnection and communication between both units 110, 120 are describedbelow. Indicator unit 120 has a contoured surface 400 that mates with amatching surface 402 of the patient attachment unit 110. The surfacesmay be of a undulating curved shape, as shown. Alternative embodimentsmay utilize crescent, linear, or other shaped surfaces. In anotherembodiment of the present invention, the contoured surface 400 of theindicator unit 120 may have a vertically-graded slope. The mating shapesof the leading surface 400 and the matching surface 402 assist inproperly securing and aligning the indicator unit 120 to the patientattachment unit 110 and help prevent inadvertent detachment of the twounits. Further, the complementary shapes of the contoured surface 400and the matching surface 402 direct the indicator unit 120 to move inand out of a locking position, to connect and disconnect the indicatorunit 120 from the patient attachment unit 110 while ensuring properalignment of the operative components.

Proximate the matching surface 402 of the patient attachment unit 110 isa mating mounting platform 404. Multiple apertures 406, 408, and 410 inthe mounting platform 404 are configured to receive corresponding matingprojections 416, 414, 352 extending from a bottom surface 120 b of theindicator unit 120 to secure the two units. The apertures 406, 408, and410 may have a polygon, oblong, or other shape. Alternativeconfigurations, shapes, and orientations of the apertures 406, 408, 410and the mating projections 416, 414, 352 are contemplated. The wells362, 364 are formed in and are substantially coterminous with the bottomsurface 120 b of the indicator unit 120. In addition, a raised lip 412circumscribes the well 362 and projects above the bottom surface 120 b.The well 362 and the lip 412 are oriented to substantially align withthe sensor membrane 302 a when the patient attachment unit 110 andindicator unit 120 are connected. The sensor membrane 302 a issubstantially coterminous with the mating mounting platform 404, and isthe top surface of the pressure chamber 302, described above. A pressureequalizing membrane 426 also may be substantially coterminous with themating mounting platform 404. The function of the pressure equalizingmembrane 426 is described below. The activation projection 428 contactsthe activation button 380 when the patient attachment unit 110 isconnected to the indicator unit 120.

Each of the projections 416, 414, 352 of the indicator unit 120 matewith the corresponding apertures 406, 408, and 410 of the patientattachment unit 110 to form the complete assembled fluid medicamentdelivery device 100. Specifically, the guiding projection 416 mates withthe guiding aperture 406; the aligning projections 414 mate with thealigning apertures 408; and the circular mating projections 352 matewith the asymmetrically oblong apertures 410. Each mating pair hascorresponding shapes and corresponding orientations to secure theindicator unit 120 to the patient attachment unit 110. Each of thecircular mating projection 352 includes an enlarged end 352 a, which isenlarged relative to an extension 352 b that projects from the exposedbottom surface 120 b of the indicator unit 120. The enlarged end 352 ais configured and sized to fit within the enlarged portion 410 a ofaperture 410. When completely installed, as described below, theextension 352 b is partially surrounded by a constricted portion 410 bof the oblong aperture 410.

The patient attachment unit 110 and the indicator unit 120 may besecured to and detached from one another as depicted in FIGS. 9A-9D.First, from the initial position depicted in FIG. 9A, the indicator unit120 is inverted (Step 1) such that the bottom surface 120 b is arrangedsubstantially opposite the mounting platform 404, as depicted in FIG.9B. The indicator unit 120 is then placed (Step 2) in close proximity tothe patient attachment unit 110, such that the enlarged ends 352 a ofthe circular mating projections 352 are aligned with and pass throughthe enlarged portions 410 a of the apertures 410. To completely securethe indicator unit 120 to the patient attachment unit 110, the patientslides (Step 3) the indicator unit 120 in an chordal direction, so thatthe extensions 352 b of the mating projections 352 are located withinthe constricted portion 410 b of the apertures 410. The enlarged ends352 a prevent the indicator unit 120 from being inadvertently dislodgedfrom the patient attachment unit 110. To disconnect the indicator unit120 from the patient attachment unit 110, the patient slides (Step 4)the indicator unit 120 in a direction opposite the direction of Step 3.Textured edge 124 may provide a gripping surface to facilitate thisstep. The enlarged ends 352 a are again aligned with the enlargedportions 410 a of the apertures 410, and the two units 110, 120 may beseparated.

The indicator unit 120 may be disconnected from the patient attachmentunit 110 in response to an occlusion event in the patent attachment unit110, or due to an electronics failure or low battery charge within theindicator unit 120. Additionally, the two units 110, 120 may bedisconnected because insulin in the patient attachment unit 110 may beexhausted or functionally depleted after prolonged use. In general, thismay occur after a period of time defined at least in part by the volumeof the elastomer reservoir 252 or the amount of insulin introduced tothe reservoir 252 during filling. In certain embodiments, the elastomerreservoir, when fully filled with insulin, may contain sufficientinsulin to dispense as needed for about 24, about 48, about 72, orgreater than about 72 hours. Other times are also contemplated, based onthe type of medicament being delivered, elastomer reservoir size,delivery schedule, etc. The separate indicator unit 120 alerts thepatient when insufficient levels of insulin remain in the patientattachment unit 110. When the insulin supply in the elastomer reservoir252 is exhausted or functionally depleted, the indicator unit 120 may bedisconnected from the patient attachment unit 110 and the patientattachment unit 110 may be disposed of. Another patient attachment unit110 may be obtained, filled with insulin and connected to the separateindicator unit 120, which may be re-used as long as it has sufficientbattery power. Alternatively, the exhausted or functionally depletedpatient attachment unit 110 may be refilled via the fill port 252.

Depicted in FIG. 10 is a cross-sectional view of the assembled fluidmedicament delivery device 100, depicting a number of internalcomponents, including the piezoelectric sounder 374, the PCB 366, thebattery 356, and the wells 362, 364. For clarify, many of the variousconduits and components contained within the patient attachment unit 110are not depicted. This figure is used to show the general matingrelationship between the two units 110, 120. When the indicator unit 120is secured to the patient attachment unit 110, the bottom surface 120 bof the indicator unit 120 is in close proximity but slightly spaced fromthe mounting platform 404, with the exception of the raised lip 412 ofthe well 362. The raised lip 412 of the well 362 contacts the sensormembrane 302 a of the patient attachment unit 110. In alternativeembodiments, other portions of the bottom surface 120 b may contact themounting platform 404. The pressure sensors 266A, 266B are mounted tothe PCB 366 and disposed in the wells 362, 364, respectively. Each wellis filled with a substance to transmit effectively pressure, forexample, a solid resilient gel 362 a, 364 a manufactured of siliconegel, for example, as manufactured by Dow Corning Corporation as productno. 3-4241. In general, silicone gels having a shore hardness of about60 Shore 00 will produce satisfactory results. Other gels may also beutilized. During manufacture, to prevent leakage of the gel at theinterface of the PCB 366 and wall of the wells 362, 364, a portion ofthe gel 362 a is placed in each well 362, 364, and allowed to solidify.The remainder of the wells 362, 364 is then completely filled with thegel 362 a, which is, in turn, allowed to harden. A meniscus 422 of thegel 362 a in the well 362 extends to the edge of the raised lip 412.Accordingly, when the patient attachment unit 110 and the indicator unit120 are connected, the meniscus 422 of the gel 362 a contacts the sensormembrane 302 a. The contact between the gel 362 a and sensor membrane302 a allows both to move in relation to one another. As fluid pressureincreases within the pressure chamber 302, the sensor membrane 302 a isforced against the meniscus 422. This pressure is transmitted throughthe gel 362 a to the sensor 266A. In an alternative manufacturingprocess, the wells 362 may be inverted and filled from the underside,with the PCB 366 placed on the wells 362 prior to curing of the gel.

Also shown in FIG. 10 is an ambient air channel 420, which is formedwhen the indicator unit 120 is attached to the patient attachment unit110. Since the mounting platform 404 and the bottom surface 120 b aregenerally not in contact, ambient air pressure may be transmitted freelyinto an interstitial space 420 a between the two units 110, 120. Thisexposes both a surface or meniscus 424 of the gel 364 a in the well 364and the pressure equalizing membrane 426 to ambient air pressure Pexternal to the device 100. This allows the device 100 to sense changesin ambient air pressure, as described below.

FIG. 11 depicts an enlarged inverted cross-sectional view of the well362. The pressure sensor 266A is mounted on the PCB 366 at the base ofthe well 362. As described above, the gel 362 a is filled to the edge ofthe raised lip 412. Three dashed lines 422A, 422B, and 422C illustratethe meniscus 422 of the gel 362 a according to various conditions. Line422A illustrates over-filling of the gel 362 a; line 422B illustratesdesired filling of the gel 362 a; line 422C illustrates under-filling ofthe gel 362 a. When the gel 362 a is filled to the desired level (i.e.,coplanar with the raised lip 412) the meniscus 422B is proximate withthe sensor membrane 302 a, while transferring little or no force betweenthe two elements. Force transmission remains minimal or nonexistentuntil fluid fills the pressure chamber 302. The raised lip 412 minimizesthe initial distance between the meniscus 422B and the sensor membrane302 a. If the gel 362 a has been over-filled, the meniscus 422A mayexert force on the sensor membrane 302 a, which may lead to inaccuratesensing. If the gel 362 a has been under-filled, the sensor membrane 302a may not contact the meniscus 422C, again leading to inaccuratesensing.

FIG. 12 depicts a simplified, schematic view of the fluid medicamentdelivery device 100 to illustrate the interrelationships between, aswell as the functionality of, the various components according to oneembodiment of the device 100. The patient attachment unit 110 includes asimplified, schematic version of the micro-fluidic circuit depicted inFIG. 3, contained within the housing 110 a. The flexible pressureequalizing membrane 426 is disposed within and substantially coterminouswith the mounting platform 404. The patient attachment unit 110 includesthe reservoir 252, for example, an elastomer bladder. The fill port 254may be used to introduce insulin into the reservoir 252. Insulindisplaced from the reservoir 252 fills the basal flowpath 262 and thebolus flowpath 264. Insulin flows through the bolus flowpath 264 andinto the patient via the cannula 282 when the bolus button 268 isactuated. Insulin in the basal flowpath 262 flows through the pressuresensor chamber 302, which includes a sensor membrane 302 a, which issubstantially coterminous with the top portion of the mounting platform404 of the patient attachment unit 110. Insulin from the basal flowpath262 and bolus flowpath 264 is introduced subcutaneously into the patientvia the cannula 282.

The simplified, schematic version of the indicator unit 120 includes thePCB 366, which is powered by the battery 352. The piezoelectric sounder374 and/or a light, such as a LED, is connected to the PCB 366. Alsomounted on the PCB 366 are the pressure sensors 266A, 266B, which areeach disposed in the wells 362, 364, respectively. The well 364 depictedon the right in FIG. 12 includes the raised lip 412. Each well 362, 364is filled with the gel 362 a, 364 a, such that the meniscus 422, 424 isformed thereon.

When the indicator unit 120 is attached to the patient attachment unit110, the ambient air channel 420 and the interstitial space 420 a isformed therebetween. Note that the various connecting elements are notdepicted. Both the meniscus 424 of the gel 364 a and the flexiblepressure equalizing membrane 426 of the patient attachment unit 110 areexposed to the ambient pressure P_(A) in the interstitial space 420 a.

As insulin in the basal flowpath 262 flows through the pressure sensorchamber 302, when insulin pressure is greater than ambient pressure, theinsulin in the filled pressure sensor chamber 302 will flex the sensormembrane 302 a outwards. This outward deflection will, in turn, applypressure to the meniscus 422 of the gel 362 a, thus transmitting thatpressure to pressure sensor 266A. The PCB 366 interprets the pressureincrease and, if required, alerts the patient, e.g., via thepiezoelectric sounder 374 and/or the light.

Changes in pressure conditions in the basal flowpath that may occur forat least several reasons: (1) due to an occlusion or partial occlusiondownstream of the pressure sensor chamber 302; (2) due to an occlusionor partial occlusion upstream of the pressure sensor chamber 302; or (3)due to a pressure spike inherent in the last phase of contraction of theelastomer reservoir 252. An occlusion or partial occlusion causes thebasal flow to stop or partially stop. A pressure spike from theelastomer reservoir 252 occurs when the reservoir 252 is approaching thelimit of the reservoir's ability to continue the flow of insulin. Duringcontraction, the elastomer reservoir 252 maintains a substantiallyconstant pressure on the insulin delivered via the basal flowpath 262.However, as the reservoir 252 nears its fully contracted state, the wallapplies move force to the insulin, temporarily increasing the pressureuntil the wall achieves a final rest condition and the insulin pressureequalizes with that of the subcutaneous pressure of the patient. Thesepressure relationships are described in more detail below.

The indicator unit 120 may be programmed to conduct a pressure readingperiodically, for example, about every 30 minutes, to monitor thefunction of the fluid medicament delivery device 100. This allows forlow power consumption and provides for longer life of the battery 352.Periodic pressure readings allow the indicator unit 120 to alert thepatient to, and differentiate between, a change in fluid pressure causedby occlusions/partial occlusions and a change in fluid pressure causedby the last contraction phase of the elastomer reservoir 252. Asdescribed in more detail below, the electronic components containedwithin the indicator unit 120 may determine that a change in pressureduring the early operational life of the device 100 is due to anocclusion (e.g., a blocked cannula 282). Further, the indicator unit 120may determine that a change in pressure during the late stages ofoperation of the device 100 is due to the last contraction phase of theelastomer reservoir 252. Regardless, upon detection of a pressure changeof a predetermined threshold valve, the patient will be alerted that thedevice 100 is not working properly and that the patient attachment unit110 needs to be replaced.

The fluid medicament delivery device 100 may operate properly in variousexternal pressure environments, for example, while a patient is atsea-level, at elevated pressure conditions (i.e., below sea-level), andat decreased pressure conditions (i.e., above sea-level). Additionally,due to the functionality described below, the components containedwithin the indicator unit 120 are able to distinguish pressure changescaused by occlusions from those caused by changes in ambient pressure.The fluid medicament delivery device 100 will continue operatingnormally in various external pressure environments and, thus, alert thepatient to changes in pressure that are only due to conditions thatrequire attention to the device 100 (e.g., an occlusion, a partialocclusion, or a near-empty condition of the elastomer bladder 252).

As described above, the indicator unit 120 includes two pressure sensors266A, 266B that are both absolute pressure sensors. When the indicatorunit 120 and patient attachment unit 110 are connected, the pressuresensor 266B is exposed to ambient air pressure P_(A). Table 1 depictsknown conditions for ambient pressure P_(A), subcutaneous (below theskin surface S) pressure P_(S) of a human body, and reservoir pressureP_(R). These pressures are given at sea-level, 1 meter below sea-level,and 3000 meters above sea-level. As an initial matter, due to thepresence of the pressure equalizing membrane 426, the ambient pressureP_(A) equals the device internal pressure P_(I). The human body is alsopressurized relative to the ambient air pressure P_(A), such that thesubcutaneous pressure P_(s) of the human body may be calculated as acombination of the ambient pressure and about 10 mbar. The reservoirpressure P_(R) exerted against the fluid contained therein may becalculated as the combination of the internal device pressure P_(I) andabout 820 mbar (i.e., the pressure exerted directly against the fluid bythe elastomer bladder material). The pressure exerted by the elastomerbladder material may be greater than or less thank 820 mbar, dependingon the material used.

TABLE 1 Known Pressures for Use in Device Operation Ambient SubcutaneousReservoir All pressures Pressure Pressure Pressure in mbar P_(A) = P_(I)P_(S) = P_(A) + 10 P_(R) = P_(I) + 820 Pressure at 1013 1023 1833Sea-Level Pressure at 1.0 1113 1123 1933 meter submersion Pressure at3000 800 810 1620 meters altitude

Further, the fluid pressure P_(F) is sensed at pressure sensor 266Abecause the meniscus 422 of the gel 362 a contacts the sensor membrane302 a of the pressure sensor chamber 302 through which the insulinflows. Table 2 depicts fluid pressures P_(F) at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level. Under Normal (i.e.,unblocked) conditions, the fluid pressure P_(F) at the pressure sensor266A is the average of the subcutaneous pressure P_(s) and the reservoirpressure P_(R). Table 2 also depicts fluid pressure P_(F) at completeocclusion and partial occlusion (so-called “half-blocking”) conditionsboth upstream and downstream of the pressure sensor chamber 302.Half-blocking conditions may occur when a flow channel or a flowrestrictor has a partial occlusion, allowing passage of inclusion atonly one-half of its rated flow rate.

TABLE 2 Fluid Pressures at Operational Conditions Upstream UpstreamDownstream Downstream All pressures Normal Occlusion Half-blockingOcclusion Half-blocking in mbar P_(F) = (P_(S) + P_(R))/2 P_(F) = P_(S)P_(F) = (2*P_(S) + P_(R))/3 P_(F) = P_(R) P_(F) = (P_(S) + 2*P_(R))/3Pressure at 1428 1023 1293 1833 1563 Sea-Level Pressure at 1528 11231393 1933 1663 1.0 meter submersion Pressure at 1215 810 1080 1620 13503000 meters altitude

Table 3 depicts pressure differentials ΔP at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level. Generally, a Normal pressuredifferential ΔP may be about 450 mbar +/−about 15%. In one embodiment, apressure differential ΔP between fluid pressure P_(F) and ambientpressure P_(A) from about 344 mbar to about 517 mbar at, below, or abovesea-level, is considered normal. A pressure differential ΔP below about344 mbar is considered a first failure state, generally caused by anupstream (of the pressure sensor chamber 302) occlusion, partialocclusion, or near-empty elastomer bladder condition. A pressuredifferential ΔP above about 517 mbar is considered a second failurestate, generally caused by a downstream (of the pressure sensor chamber302) occlusion or partial occlusion. The uniform pressure differentialsfor each failure condition (i.e., upstream and downstream occlusion,upstream and downstream half-blocking) allow the device to differentiatebetween the various failure conditions. Information regarding thevarious failure conditions may be stored in the components within theindicator unit 120, for later download to a computer fordevice-diagnostic or other purposes.

TABLE 3 Pressure Differentials at Operational Conditions UpstreamUpstream Downstream Downstream All pressures Normal OcclusionHalf-blocking Occlusion Half-blocking in mbar ΔP = P_(F) − P_(A) ΔP =P_(F) − P_(A) ΔP = P_(F) − P_(A) ΔP = P_(F) − P_(A) ΔP = P_(F) − P_(A)Pressure at Sea-Level 415 10 280 820 550 Pressure at 1.0 meter 415 10280 820 550 submersion Pressure at 3000 meters 415 10 280 820 550altitude

The pressure-equalizing membrane 426 allows the device to accuratelysense pressures and analyze the various pressure conditions duringoperation, either at, above, or below sea-level. Consider a proposedinsulin infusion device that lacks a pressure equalizing membrane(depicted as 426 in FIG. 12). Table 4 depicts known conditions forambient pressure P_(A), internal device pressure P_(I), subcutaneouspressure P_(S) of a human, and reservoir pressure P_(R). These pressuresare given at sea-level, 1 meter below sea-level, and 3000 meters abovesea-level. Since a pressure equalizing membrane is not utilized, theinternal device pressure P_(I) remains constant (in this case, at theenvironmental pressure at which the device was manufactured, e.g.,sea-level). In certain devices, the internal pressure P_(I) may beelevated, if the device was manufactured in a clean room, for example,which typically has a pressure higher than the ambient pressure of thelocation where the clean room is contained. Regardless, this constantinternal pressure P_(I) has a direct effect on the reservoir pressureP_(R), as shown in Table 4.

TABLE 4 Known Pressures for Use in Device Operation (NoPressure-Equalizing Membrane) Ambient Internal Subcutaneous ReservoirAll pressures in Pressure Pressure Pressure Pressure mbar P_(A) P_(I)P_(S) = P_(A) + 10 P_(R) = P_(I) + 820 Pressure at 1013 1013 1023 1833Sea-Level Pressure at 1.0 1113 1013 1123 1833 meter submersion Pressureat 3000 800 1013 810 1820 meters altitude

Table 5 depicts fluid pressures P_(F) at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level, for a device lacking apressure-equalizing membrane. Fluid pressure P_(F) at complete occlusionand partial occlusion conditions upstream and downstream of the pressuresensor chamber 302 are also depicted in Table 5.

TABLE 5 Fluid Pressures at Operational Conditions (NoPressure-Equalizing Membrane) Upstream Upstream Downstream DownstreamAll pressures Normal Occlusion Half-blocking Occlusion Half-blocking inmbar P_(F) = (P_(S) + P_(R))/2 P_(F) = P_(S) P_(F) = (2*P_(S) + P_(R))/3P_(F) = P_(R) P_(F) = (P_(S) + 2*P_(R))/3 Pressure at 1428 1023 12931833 1563 Sea-Level Pressure at 1478 1123 1360 1833 2395 1.0 metersubmersion Pressure at 3000 1322 810 1151 1833 1492 meters altitude

Table 6 depicts pressure differentials ΔP at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level. As described above, a Normalpressure differential ΔP may be defined as about 450 mbar +/−about 15%.That is, a pressure differential ΔP from about 344 mbar to about 517mbar at, below, or above sea-level is considered normal. A pressuredifferential ΔP below about 344 mbar is considered a first failurestate; a pressure differential ΔP above about 517 mbar is considered asecond failure state. The pressure differentials depicted in Table 6show the advantages provided by a infusion device that includes apressure-equalizing membrane, such as that used with the devicedescribed herein. Absence of the pressure equalizing membrane may causeat least three types of problems. First, pressure differentials underNormal (i.e., unblocked) conditions may register as a failure condition(where a failure condition is defined as a pressure differential inexcess of 517 mbar). See, for example, the Normal condition pressure at3000 meters altitude, which is an operational altitude for an airplane.In such a case, the device is operating normally, but the deviceinterprets the pressure differential as a failure condition. The devicewould signal the patient that the device is not operating properly,which may cause the patient to remove and replace a device that isotherwise operating properly.

Second, a condition that should be interpreted as a failure conditionmay be overlooked. See, for example, the Upstream Half-blockingcondition pressure at 3000 meters altitude. There, the pressuredifferential falls within the normal range of about 344 mbar to 517mbar. Thus, the device would not alert the patient to a failureconditions, even though there is blockage within the fluid circuit. Thismay cause a serious medical condition. Third, as can be seen, thepressure differentials are not consistent across the same failureconditions, which would prevent the particular failure condition frombeing subsequently identified during diagnostics.

TABLE 6 Pressure Differentials at Operational Conditions (NoPressure-Equalizing Membrane) Upstream Upstream Downstream DownstreamAll pressures Normal Occlusion Half-blocking Occlusion Half-blocking inmbar ΔP = P_(F) − P_(A) ΔP = P_(F) − P_(A) ΔP = P_(F) − P_(A) ΔP = P_(F)− P_(A) ΔP = P_(F) − P_(A) Pressure at Sea-Level 415 10 280 820 550Pressure at 1.0 meter 365 10 247 720 1282 submersion Pressure at 3000meters  522* 10  351* 1033 692 altitude

FIG. 13A depicts a perspective view of a fluid medicament deliverydevice 100 in accordance with an embodiment of the invention. FIGS.13B-13C depict a procedure for using the fluid medicament deliverydevice 100. The fluid medicament delivery device 100 includes thepatient attachment unit 110 and the separate indicator unit 120. Ahousing for the cannula insertion device 450 and the bolus button 268are disposed on the patient attachment unit 110. An adhesive tape 452for adhering the device 100 to the skin of a patient is disposed on theunderside of the patient attachment unit 110. A liner 454 is included tocover the adhesive tape 452 before the device 100 is attached to thepatient.

The device 100 is first removed its packaging (Step 500) which keeps thedevice 100 clean during storage and transport, prior to use. Theseparate indicator unit 120 is mounted to the patient attachment unit100 (Step 502), for example, in the manner described above and shown inFIGS. 9A-9C. To fill the device 100 with insulin (Step 504), an insulinpen 254 a is connected to a fill port 254 on the underside of thepatient attachment unit 110. Insulin is then dispensed from the pen 254a to fill the insulin reservoir (Step 506). Once full, the insulin pen254 a is disconnected from the device 100 and discarded (Step 508). Theliner 454 is then removed from the device 100 to expose the adhesivetape (Step 510). The patient attachment unit 100 is then adhered to anappropriate portion of the patient's skin S (Step 512). Acceptablelocations include, but are not limited to, the abdominal area, the areaabove the buttocks, or the area proximate the triceps muscle. Thepatient then actuates the cannula insertion device 450 to insert thecannula into the body (Step 514). The patient disconnects the housing ofthe cannula insertion device 450 from the patient attachment unit 110(Step 516). The device 100 is now operational and may be worn by thepatient during normal, everyday activities. When the device 100 needs tobe removed (either due to a failure state or depletion of insulin), thepatient peels the device 100 from the skin S (Step 518). As shown inStep 520, the patient may then detach the indicator unit 120 from thepatient attachment unit 110, as described above with regard to FIG. 9D.The indicator unit 120 may then be attached to a new patient attachmentunit 110′. In this way, the comparatively more-expensive indicator unit120 may be reused, while the less-expensive patient attachment unit 110may be disposed of.

The various components utilized in the device described herein may bemetal, glass, and/or any type of polymer suitable for sterilization anduseful for delivering insulin or other medicaments subcutaneously.Polyurethane, polypropylene, PVC, PVDC, EVA, and others, arecontemplated for use, as are stainless steel and other medical-grademetals. More specifically, medical-grade plastics may be utilized forthe cannula itself, as well as other components that contact orotherwise penetrate the body of the patient. Needles and springs madefrom medical-grade stainless steel are also desirable, to preventfailure associated with use.

While there have been described herein what are to be consideredexemplary and preferred embodiments of the present invention, othermodifications of the invention will become apparent to those skilled inthe art from the teachings herein without departing from the spirit oressential characteristics thereof. The present embodiments are thereforeto be considered in all respects as illustrative and not restrictive.The particular methods of manufacture and geometries disclosed hereinare exemplary in nature and are not to be considered limiting. It istherefore desired to be secured in the appended claims all suchmodifications as fall within the spirit and scope of the invention.Accordingly, what is desired to be secured by Letters Patent is theinvention as defined and differentiated in the following claims, and allequivalents.

The invention claimed is:
 1. A fluid medicament delivery devicecomprising: a patient attachment unit comprising a housing and a fluidchannel located therein, wherein at least a portion of the fluid channelcomprises a flexible member substantially coterminous with the housing;a separate indicator unit adapted to be detachably coupled to thehousing of the patient attachment unit, the indicator unit comprising afirst sensing element for contacting the flexible member when theindicator unit is coupled to the housing, wherein the first sensingelement senses a flexure of the flexible member; and a equalizingmembrane exposed to an ambient pressure external to the housing, whereinthe equalizing membrane is adapted for enabling analysis of variouspressure conditions during operation at different ambient pressures. 2.The fluid medicament delivery device of claim 1, wherein the indicatorunit further comprises a second sensing element for sensing the ambientpressure.
 3. The fluid medicament delivery device of claim 2, whereinthe second sensing element comprises a pressure sensor adapted to sensethe ambient pressure, and at least one of a fluid and a gel adapted totransmit the ambient pressure to the pressure sensor.
 4. The fluidmedicament delivery device of claim 1, wherein the first sensing elementcomprises a pressure sensor.
 5. The fluid medicament delivery device ofclaim 4, wherein the first sensing element further comprises at leastone of a fluid and a gel adapted to contact the flexible member, whereinthe flexure of the flexible member is transmitted by the at least one ofthe fluid and the gel to the pressure sensor.
 6. The fluid medicamentdelivery device of claim 5, wherein the separate indicator unit definesa well for containing at least one of the liquid and the gel.
 7. Thefluid medicament delivery device of claim 6, wherein the separateindicator unit comprises a raised lip surrounding the well, wherein theraised lip is disposed above a proximate portion of the separateindicator unit.
 8. The fluid medicament delivery device of claim 7,wherein the raised lip is adapted to contact the housing of the patientattachment unit.
 9. The fluid medicament delivery device of claim 1,wherein the housing comprises a hermetically-sealed housing defining aninterior space and comprising the equalizing membrane, the equalizingmembrane adapted for transmitting the ambient pressure to the interiorspace.
 10. The fluid medicament delivery device of claim 9, wherein theequalizing membrane is located on a portion of the patient attachmentunit facing the separate indicator unit and wherein the second sensingelement is located on a portion of the separate indicator unit facingthe patient attachment unit, when the patient attachment unit is coupledto the separate indicator unit.
 11. The fluid medicament delivery deviceof claim 1, wherein the patient attachment unit is adapted for adhesionto a skin surface of a patient.
 12. The fluid medicament delivery deviceof claim 1, further comprising a processor adapted for interpreting asignal from a pressure sensor, wherein the signal is sent to theprocessor based at least in part on the flexure of the flexible member.13. A method of monitoring pressure within a fluid channel of a fluidmedicament delivery device, the method comprising: measuring an actualpressure of a fluid within the fluid channel across a flexible member;equalizing an ambient pressure external to the device and an internalpressure across a equalizing membrane; measuring the ambient pressureexternal to the device; calculating a pressure differential based on theactual pressure and the ambient pressure; comparing the pressuredifferential to a pressure range comprising a maximum pressuredifferential and a minimum pressure differential; and sending anotification when the pressure differential is outside of the pressurerange.
 14. The method of claim 13, further comprising: modifying thepressure differential based on the ambient pressure to obtain acorrected pressure differential; and comparing the corrected pressuredifferential to the pressure range.
 15. The method of claim 13, furthercomprising: modifying the maximum pressure differential and a minimumpressure differential of the pressure range based on the ambientpressure to obtain a corrected pressure range; and comparing thecorrected pressure range to the pressure differential.
 16. The method ofclaim 13, wherein when the pressure differential exceeds the maximumpressure differential, the notification comprises at least one of adownstream occlusion notification and a near-empty reservoirnotification.
 17. The method of claim 13, wherein when the pressuredifferential is less than the minimum pressure differential, thenotification comprises at least one of an upstream occlusionnotification and an empty reservoir notification.